INFLUENZA OVERVIEW AND CLINICAL EXPERIENCE WITH NOVEL H1N1 IN MONTEREY COUNTY

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INFLUENZA OVERVIEW AND CLINICAL EXPERIENCE
WITH NOVEL H1N1 IN MONTEREY COUNTY

• Allen Radner, M.D.

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Outline

• Basic Virology
• Epidemiology
• Pandemics
• Clinical Manifestations
• Clinical Observations in Monterey County 2009

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VIRAL STRUCTURE

• Orthomyxiviridae
• Envelope HA and NA glycoproteins
• Matrix (M) protein (M2)
• Internal Nucleocapsid 8 SS RNA
  segments/polymerases

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STRUCTURE-FUNCTION RELATIONSHIPS

• Glycoprotein Functions
• Relative species specificity
• Antiviral Activity
• NA inhibitors
• M2 blockers

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STRUCTURE-FUNCTION RELATIONSHIPS

• Immunity
• Vaccines
• Virulence Factors
• Polybasic aa segments on HA
• PB1-F2

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INFLUENZA

• 3 Major Types
• Subtypes and Strains
• Antigenic Drift
• Antigenic Shift
• Nomenclature
• A/Brisbane/57/2007(H1N1-like), A/Brisbane/10/2007(
  H3N2-like), B/Florida/4/2006
• A/Mexico/2009 (H1N1)
• Triple reassortment of swine, avian, human origin

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EPIDEMIOLOGY

• Virus circulates the globe.
• Introduction of new strains.
• Mutations
• Introduction of strains from Animal Reservoirs.
• Endemics, epidemics, pandemics.

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PANDEMIC INFLUENZA

• Requirements for Development
• 1. Introduction of a new virus into a population
  without immunity.
• 2. Virus causes human illness
• 3. Efficient spread human to human.
• Characteristics
• Rapid spread, independent of season, successive
  waves, high mortality in healthy young adults.
• Successive waves

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PANDEMIC INFLUENZA

• 1918-1919 Spanish Flu
• 20-40 million deaths, 2 billion infected
• H1N1
• 1957-59 Asian Flu
• 1 million deaths, 1 billion infected
• H2N2
• 1968-69 Hong Kong Flu
• 500,000 deaths
• H3N2
• Novel H1N1 Influenza A
• Avian H5N1

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CLINICAL MANIFESTATIONS

• Respiratory Tract Infection
• Acute onset fever, cough, myalgias, headache,
  malaise
• Less frequently coryza, sore throat, GI
  symptoms.
• Usually self-limited

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COMPLICATIONS

• RAD/COPD exacerbations
• Primary Influenza Pneumonia
• Early
• Valvular heart dz/Pregnancy
• Secondary Bacterial Pneumonia
• 5-7 days into illness
• Elderly, co morbidities
• S. aureus, S. pyogenes, S. pneumoniae
• Combined

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COMPLICATIONS

• Myositis, myocarditis, pericarditis,
  encephalopathy, myelitis, GBS, Reyes Syndrome
• Septic Shock

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ICU Patients Monterey Co. 2009
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OBSERVATIONS

• 1. Most patients do well.
• 2. Significant (???) percentage with severe
  disease.
• 3. Primary Co-morbidity of Obesity
• 4. Relatively young patients.
• 5. Severe disease characterized by profound
  hypoxemia with prolonged ventilatory support
  requirements.
• 6. Critical illness polyneuropathy/myopathy.
• 7. All with negative RIDTs.
• 8. Associated bacterial superinfections

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QUESTIONS

• 1. Communicability
• Public Health/Infection control
• 2. Diagnostic capabilities
• 3. Therapeutic options